TFT substrate structure

ABSTRACT

The present invention provides a TFT substrate structure, comprising a Switching TFT and a Driving TFT, and the Switching TFT comprises a first active layer, and the Driving TFT comprises a second active layer, and the first active layer and the second active layer are made by the same or different materials and the electrical properties of the Switching TFT and the Driving TFT are different. According to the different functions of the different TFTs, the present invention employs different working structures for the Switching TFT and the Driving TFT to respectively implement deposition and photolithography, and employs different materials for the active layers of the Switching TFT and the Driving TFT to differentiate the electrical properties of different TFTs in the TFT substrate. Accordingly, the accurate control to the OLED with lowest cost can be realized.

FIELD OF THE INVENTION

The present invention relates to a display technology field, and moreparticularly to a TFT substrate structure.

BACKGROUND OF THE INVENTION

Active Matrix/Organic Light Emitting Diode (AMOLED) is so called nextgeneration display technology. The AMOLED possesses fast response speed,wide view angle, high contrast, et cetera in comparison with traditionalTFT-LCD. The driving of OLED requires higher mobility for the backplateTFT. At present, the mobility of the developed amorphous silicon (a-Si)merely can reach up to 0.5˜0.8 cm²/Vs, which cannot satisfy the normaldriving of OLED. The Low Temperature Poly-silicon (LTPS) and the metaloxide semiconductor (such as IGZO) with higher mobility can be theresearch point for the thin film transistor (TFT) of the active layer.

In AMOLED, the OLED is driven by the thin film transistor (TFT) in thebackplate. The backplate TFTs can be categorized as the Switching TFTand the Driving TFT. The Switching TFT is only for realizing theswitching function. Thus, TFTs of low price and stable process can beutilized. However, the Driving TFT demands enough mobility for realizingthe driving of the OLED. The TFTs with larger mobility can be utilizedtherefor.

According to the traditional OLED backplate process at present, the samestructure and process order are employed for the Switching TFT and theDriving TFT, which the active layer utilizes only one kind of material(metal oxide semiconductor or LTPS). It is difficult to achieve thedifferentiations of the two kinds of TFTs of different functions. On theother hand, the Switching TFT, the Driving TFT and the capacitor in onepixel are independent from one another, which is a disadvantage forincrease of the aperture ratio.

A common 2T1C structure (two TFTs and one storage capacitor) of drivingOLED is shown in FIG. 1: the two TFTs 101, 102 are both the etchingstopper layer (ESL) structure. The active layers 201, 202 utilize onekind of material (the metal oxide semiconductor or the LTPS). Totally,five masks are required for accomplishing the passivation layer 600.Meanwhile, after the same manufacture process, the TFTs 101, 102 possessthe same electrical properties.

SUMMARY OF THE INVENTION

An objective of the present invention is to provide a TFT substratestructure. According to the different functions of the different TFTs,the present invention employs different working structures for theSwitching TFT and the Driving TFT to respectively implement depositionand photolithography, and employs different materials for the activelayers of the Switching TFT and the Driving TFT to differentiate theelectrical properties of different TFTs in the TFT substrate.Accordingly, the accurate control to the OLED with lowest cost can berealized.

For realizing the aforesaid objectives, the present invention provides aTFT substrate structure, comprising a Switching TFT and a Driving TFT,and the Switching TFT comprises a first active layer, and the DrivingTFT comprises a second active layer, and the first active layer and thesecond active layer are made by the same or different materials and theelectrical properties of the Switching TFT and the Driving TFT aredifferent.

The TFT substrate comprises a substrate, a first active layer formed onthe substrate, a first metal layer formed on the substrate and the firstactive layer, a first insulation layer formed on the first active layerand the first metal layer, and covering the substrate, a second activelayer formed on the first insulation layer, a second metal layer formedon the first insulation layer, a third metal layer formed on the secondactive layer and the first insulation layer, a passivation layer formedon the second active layer and the third metal layer, and covering thefirst insulation layer, and a pixel electrode layer formed on thepassivation layer, and contacting the third metal layer.

The TFT substrate comprises a substrate, a first metal layer formed onthe substrate, a first insulation layer formed on the first metal layer,and covering the substrate and the first metal layer, a first activelayer formed on the first insulation layer, a second metal layer formedon the first active layer and the first insulation layer, a secondinsulation layer formed on the second metal layer and the first activelayer, and covering the first insulation layer, a second active layerformed on the second insulation layer, a third metal layer formed on thesecond active layer and the second insulation layer, a passivation layerformed on the second active layer and the third metal layer, andcovering the second insulation layer, and a pixel electrode layer formedon the passivation layer and contacting the third metal layer.

The TFT substrate comprises a substrate, a first metal layer formed onthe substrate, a first insulation layer formed on the first metal layer,a second metal layer formed on the first insulation layer, a firstactive layer formed on the second metal layer and contact the firstinsulation layer, a second insulation layer formed on the first activelayer and the second metal layer, and covering the first insulationlayer, a second active layer formed on the second insulation layer, athird metal layer formed on the second active layer and the secondinsulation layer, a passivation layer formed on the second active layerand the third metal layer, and covering the second insulation layer, anda pixel electrode layer formed on the passivation layer and contactingthe third metal layer.

The TFT substrate comprises a substrate, a first metal layer formed onthe substrate, a first insulation layer formed on the first metal layer,and covering the substrate and the first metal layer, a first activelayer formed on the first insulation layer, an etching stopper layerformed on the first active layer, a second metal layer formed on thefirst insulation layer and the etching stopper layer, and covering thefirst active layer, a second insulation layer formed on the second metallayer, and covering the first insulation layer, a second active layerformed on the second insulation layer, a third metal layer formed on thesecond insulation layer, and covering two ends of the second activelayer, a passivation layer formed on the third metal layer and thesecond active layer, and covering the second insulation layer, and apixel electrode layer formed on the passivation layer and contacting thethird metal layer.

Material of the first active layer and material of the second activelayer respectively are amorphous silicon and metal oxide semiconductor,Low Temperature Poly-silicon and amorphous silicon, Low TemperaturePoly-silicon and metal oxide semiconductor, or both metal oxidesemiconductor.

The TFT substrate comprises a substrate, a first metal layer formed onthe substrate, a first insulation layer formed on the first metal layer,and covering the substrate and the first metal layer, a first activelayer formed on the first insulation layer, a second metal layer formedon two ends of the first active layer and the first insulation layer, asecond insulation layer formed on the first active layer and the secondmetal layer, and covering the first insulation layer, a third metallayer formed on the second insulation layer, a second active layerformed on the third metal layer and contacting the second insulationlayer, a passivation layer formed on the third metal layer and thesecond active layer, and covering the second insulation layer, and apixel electrode layer formed on the passivation layer and contacting thethird metal layer; the first active layer and the second active layerare at the same side of the substrate.

Material of the first active layer and material of the second activelayer respectively are amorphous silicon and metal oxide semiconductoror both metal oxide semiconductor.

The present invention further provides a TFT substrate structure,comprising a Switching TFT and a Driving TFT, and the Switching TFTcomprises a first active layer, and the Driving TFT comprises a secondactive layer, and the first active layer and the second active layer aremade by the same or different materials and the electrical properties ofthe Switching TFT and the Driving TFT are different;

wherein the TFT substrate comprises a substrate, a first active layerformed on the substrate, a first metal layer formed on the substrate andthe first active layer, a first insulation layer formed on the firstactive layer and the first metal layer, and covering the substrate, asecond active layer formed on the first insulation layer, a second metallayer formed on the first insulation layer, a third metal layer formedon the second active layer and the first insulation layer, a passivationlayer formed on the second active layer and the third metal layer, andcovering the first insulation layer, and a pixel electrode layer formedon the passivation layer, and contacting the third metal layer;

wherein material of the first active layer and material of the secondactive layer respectively are amorphous silicon and metal oxidesemiconductor, Low Temperature Poly-silicon and amorphous silicon, LowTemperature Poly-silicon and metal oxide semiconductor, or both metaloxide semiconductor.

The benefits of the present invention are: the present inventionprovides a TFT substrate structure. According to the different functionsof the different TFTs, the present invention employs different workingstructures for the Switching TFT and the Driving TFT to respectivelyimplement deposition and photolithography, and employs differentmaterials for the active layers of the Switching TFT and the Driving TFTto differentiate the electrical properties of different TFTs in the TFTsubstrate. Accordingly, the accurate control to the OLED with lowestcost can be realized. The process is simple. The manufacture cost islow. By stacking-up deposing the TFTs with different functions, theaperture ratio is increased.

BRIEF DESCRIPTION OF THE DRAWINGS

The technical solution and the beneficial effects of the presentinvention are best understood from the following detailed descriptionwith reference to the accompanying figures and embodiments.

In drawings,

FIG. 1 is a structural diagram of a TFT substrate according to priorart;

FIG. 2 is a structural diagram of a TFT substrate structure according tothe first embodiment of the present invention;

FIG. 3 is a structural diagram of a TFT substrate structure according tothe second embodiment of the present invention;

FIG. 4 is a structural diagram of a TFT substrate structure according tothe third embodiment of the present invention;

FIG. 5 is a structural diagram of a TFT substrate structure according tothe fourth embodiment of the present invention;

FIG. 6 is a structural diagram of a TFT substrate structure according tothe fifth embodiment of the present invention;

FIG. 7 shows electric property curve diagrams of the metal oxidesemiconductor TFTs of the TFT substrate structure according to thepresent invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

For better explaining the technical solution and the effect of thepresent invention, the present invention will be further described indetail with the accompanying drawings and the specific embodiments.

The present invention provides a TFT substrate structure, comprising aSwitching TFT and a Driving TFT, and the Switching TFT comprises a firstactive layer, and the Driving TFT comprises a second active layer, andthe first active layer and the second active layer are made by the sameor different materials and the electrical properties of the SwitchingTFT and the Driving TFT are different.

Please refer to FIG. 2. The TFT substrate structure according to thefirst embodiment of the present invention is a combination formation ofa top gate structure and a back channel etching (BCE) structure.Specifically, the TFT substrate structure comprises a substrate 1, afirst active layer 21 formed on the substrate 1, a first metal layer 31formed on the substrate 1 and the first active layer 21, a firstinsulation layer 41 formed on the first active layer 21 and the firstmetal layer 31, and covering the substrate 1, a second active layer 22formed on the first insulation layer 41, a second metal layer 32 formedon the first insulation layer 41, a third metal layer 33 formed on thesecond active layer 22 and the first insulation layer 41, a passivationlayer 6 formed on the second active layer 22 and the third metal layer33, and covering the first insulation layer 41, and a pixel electrodelayer 7 formed on the passivation layer 6, and contacting the thirdmetal layer 33.

Specifically, in this structure, the left side of the first metal layer31 is a source/a drain of a TFT 11, the right side is a gate of a TFT12, i.e. the gate of the TFT 12 and the drain of the TFT 11 areconnected. The second metal layer 32 is a gate of the TFT 11, and thethird metal layer 33 is a source/a drain of the TFT 12.

Please refer to FIG. 3. The TFT substrate structure according to thesecond embodiment of the present invention is a combination formation oftwo back channel etching (BCE) structures. Specifically, the TFTsubstrate structure comprises a substrate 1, a first metal layer 31formed on the substrate 1, a first insulation layer 41 formed on thefirst metal layer 31, and covering the substrate 1 and the first metallayer 31, a first active layer 21 formed on the first insulation layer41, a second metal layer 32 formed on the first active layer 31 and thefirst insulation layer 41, a second insulation layer 42 formed on thesecond metal layer 32 and the first active layer 21, and covering thefirst insulation layer 41, a second active layer 22 formed on the secondinsulation layer 42, a third metal layer 33 formed on the second activelayer 22 and the second insulation layer 42, a passivation layer 6formed on the second active layer 22 and the third metal layer 33, andcovering the second insulation layer 42, and a pixel electrode layer 7formed on the passivation layer 6 and contacting the third metal layer33.

Specifically, in this structure, the first metal layer 31 is a gate of aTFT 11, the left side of the second metal layer 32 is a source/a drainof a TFT 11, and the right side is a gate of the TFT 12, i.e. the gateof the TFT 12 and the drain of the TFT 11 are connected. The third metallayer 33 is a source/a drain of the TFT 12.

Please refer to FIG. 4. The TFT substrate structure according to thethird embodiment of the present invention is a combination formation ofa Co-planar structure and a back channel etching (BCE) structure.Specifically, the TFT substrate structure comprises a substrate 1, afirst metal layer 31 formed on the substrate 1, a first insulation layer41 formed on the first metal layer 31, a second metal layer 32 formed onthe first insulation layer 41, a first active layer 21 formed on thesecond metal layer 32 and contact the first insulation layer 41, asecond insulation layer 42 formed on the first active layer 21 and thesecond metal layer 32, and covering the first insulation layer 41, asecond active layer 22 formed on the second insulation layer 42, a thirdmetal layer 33 formed on the second active layer 22 and the secondinsulation layer 42, a passivation layer 6 formed on the second activelayer 22 and the third metal layer 33, and covering the secondinsulation layer 42, and a pixel electrode layer 7 formed on thepassivation layer 6 and contacting the third metal layer 33.

Specifically, in this structure, the first metal layer 31 is a gate of aTFT 11, the left side of the second metal layer 32 is a source/a drainof a TFT 11, and the right side is a gate of the TFT 12, i.e. the gateof the TFT 12 and the drain of the TFT 11 are connected. The third metallayer 33 is a source/a drain of the TFT 12.

Significantly, in the TFT substrate shown in FIG. 4, the first TFT 11employs a formation of the Co-planar structure (Co-planar), and thesecond TFT 12 employs a formation of the back channel etching (BCE).Similarly, the first TFT 11 can employ a formation of the back channeletching (BCE), while the second TFT 12 employs a formation of theCo-planar structure (Co-planar).

Please refer to FIG. 5. The TFT substrate structure according to thefourth embodiment of the present invention is a combination formation ofan etching stopper layer (ESL) and a back channel etching (BCE)structure. Specifically, the TFT substrate structure comprises asubstrate 1, a first metal layer 31 formed on the substrate, a firstinsulation layer 41 formed on the first metal layer 31, and covering thesubstrate 1 and the first metal layer 41, a first active layer 21 formedon the first insulation layer 41, an etching stopper layer 5 formed onthe first active layer 21, a second metal layer 32 formed on the firstinsulation layer 41 and the etching stopper layer 5, and covering thefirst active layer 21, a second insulation layer 42 formed on the secondmetal layer 32, and covering the first insulation layer 41, a secondactive layer 22 formed on the second insulation layer 42, a third metallayer 33 formed on the second insulation layer 42, and covering two endsof the second active layer 22, a passivation layer 6 formed on the thirdmetal layer 33 and the second active layer 22, and covering the secondinsulation layer 42, and a pixel electrode layer 7 formed on thepassivation layer band contacting the third metal layer 33.

Specifically, in this structure, the first metal layer 31 is a gate of aTFT 11, the left side of the second metal layer 32 is a source/a drainof a TFT 11, and the right side is a gate of the TFT 12, i.e. the gateof the TFT 12 and the drain of the TFT 11 are connected. The third metallayer 33 is a source/a drain of the TFT 12.

Significantly, in the TFT substrate shown in FIG. 5, the first TFT 11employs a formation of the etching stopper layer (ESL), and the secondTFT 12 employs a formation of the back channel etching (BCE). Similarly,the first TFT 11 can employ a formation of the back channel etching(BCE), while the second TFT 12 employs a formation of the etchingstopper layer (ESL).

Furthermore, in the aforesaid first to fourth embodiments of the TFTsubstrate, material of the first active layer 21 and material of thesecond active layer 22 respectively are amorphous silicon (a-Si) andmetal oxide semiconductor, Low Temperature Poly-silicon (LTPS) andamorphous silicon (a-Si), or both metal oxide semiconductor. Besides, inthe aforesaid first embodiment, the material of the second active layer22 respectively can be Low Temperature Poly-silicon (LTPS) and metaloxide semiconductor.

Preferably, material of the oxide semiconductor can be Indium GalliumZinc Oxide (IGZO).

Please refer to FIG. 6. The TFT substrate structure according to thefifth embodiment of the present invention is a combination formation ofa Co-planar structure and a back channel etching (BCE) structure.Specifically, the TFT substrate structure comprises a substrate 1, afirst metal layer 31 formed on the substrate 1, a first insulation layer41 formed on the first metal layer 31, and covering the substrate 1 andthe first metal layer 31, a first active layer 21 formed on the firstinsulation layer 41, a second metal layer 32 formed on two ends of thefirst active layer 21 and the first insulation layer 41, a secondinsulation layer 42 formed on the first active layer 21 and the secondmetal layer 32, and covering the first insulation layer 41, a thirdmetal layer 33 formed on the second insulation layer 42, a second activelayer 22 formed on the third metal layer 33 and contacting the secondinsulation layer 42, a passivation layer 6 formed on the third metallayer 33 and the second active layer 22, and covering the secondinsulation layer 42, and a pixel electrode layer 7 formed on thepassivation layer 6 and contacting the third metal layer 33; the firstactive layer 21 and the second active layer 22 are at the same side ofthe substrate 1. By stacking-up deposing the TFTs with differentfunctions, the occupied area of TFTs is diminished and the apertureratio is increased.

Furthermore, material of the first active layer 21 and material of thesecond active layer 22 respectively are amorphous silicon (a-Si) andmetal oxide semiconductor, or both metal oxide semiconductor.Preferably, material of the oxide semiconductor can be Indium GalliumZinc Oxide (IGZO).

FIG. 7 shows electric property curve diagrams of the metal oxidesemiconductor TFTs of the TFT substrate structure according to thepresent invention. It verifies that differentiations do exist betweenthe Switching TFT and the Driving TFT in the TFT substrate of thepresent invention.

In the experiment and verification, both the active layers of theSwitching TFT and the Driving TFT employ oxide semiconductor material.By changing the condition parameters of the experiments, thedifferentiations of the electrical properties of the two are achievedultimately. Specifically, as shown in FIG. 7, (a) and (b) can realizethe differentiation of S.S; (a) and (c) can realize the differentiationof Vth (similar to Vg to realize one TFT on and on TFT off) and also canbe applied in other circuits; (a) and (d) can realize thedifferentiation of Ion. Therefore, the TFT substrate structure of thepresent invention can differentiate the electrical properties ofdifferent TFTs.

In conclusion, the present invention provides a TFT substrate structure.According to the different functions of the different TFTs, the presentinvention employs different working structures for the Switching TFT andthe Driving TFT to respectively implement deposition andphotolithography, and employs different materials for the active layersof the Switching TFT and the Driving TFT to differentiate the electricalproperties of different TFTs in the TFT substrate. Accordingly, theaccurate control to the OLED with lowest cost can be realized. Theprocess is simple. The manufacture cost is low. By stacking-up deposingthe TFTs with different functions, the aperture ratio is increased.

Above are only specific embodiments of the present invention, the scopeof the present invention is not limited to this, and to any persons whoare skilled in the art, change or replacement which is easily derivedshould be covered by the protected scope of the invention. Thus, theprotected scope of the invention should go by the subject claims.

What is claimed is:
 1. A thin-film transistor (TFT) substrate structure,comprising a Switching TFT and a Driving TFT, and the Switching TFTcomprises a first active layer, and the Driving TFT comprises a secondactive layer, and the first active layer and the second active layer aremade by the same or different materials and the electrical properties ofthe Switching TFT and the Driving TFT are different; wherein the TFTsubstrate comprises a substrate, a first active layer formed on thesubstrate, a first metal layer formed on the substrate and the firstactive layer, a first insulation layer formed on the first active layerand the first metal layer, and covering the substrate, a second activelayer formed on the first insulation layer, a second metal layer formedon the first insulation layer, a third metal layer formed on the secondactive layer and the first insulation layer, a passivation layer formedon the second active layer and the third metal layer, and covering thefirst insulation layer, and a pixel electrode layer formed on thepassivation layer, and contacting the third metal layer; wherein thefirst insulation layer is located between the first metal layer and thesecond metal layer and is also located between the first metal layer andthe third metal layer such that the first insulation layer is a gateinsulation layer that isolates the first active layer from the secondmetal layer and also isolates the first metal layer from the secondactive layer; and wherein the first metal is in contact engagement withthe first active and is separated from the second active layer by thefirst insulation layer; the second metal layer is separated from thefirst active layer and the first metal layer by the first insulationlayer, and is also separated from the second active layer; and the thirdmetal layer is in contact engagement with the second active layer,wherein the Switching TFT that comprises the first active layer alsocomprises the second metal layer and a part of the first metal layer andthe Driving TFT that comprises the second active layer also comprisesthe third metal layer and a part of the first metal layer.
 2. The TFTsubstrate structure according to claim 1, wherein material of the firstactive layer and material of the second active layer respectively areamorphous silicon and metal oxide semiconductor, Low TemperaturePoly-silicon and amorphous silicon, Low Temperature Poly-silicon andmetal oxide semiconductor, or both metal oxide semiconductor.
 3. Athin-film transistor (TFT) substrate structure, comprising a SwitchingTFT and a Driving TFT, and the Switching TFT comprises a first activelayer, and the Driving TFT comprises a second active layer, and thefirst active layer and the second active layer are made by the same ordifferent materials and the electrical properties of the Switching TFTand the Driving TFT are different; wherein the TFT substrate comprises asubstrate, a first active layer formed on the substrate, a first metallayer formed on the substrate and the first active layer, a firstinsulation layer formed on the first active layer and the first metallayer, and covering the substrate, a second active layer formed on thefirst insulation layer, a second metal layer formed on the firstinsulation layer, a third metal layer formed on the second active layerand the first insulation layer, a passivation layer formed on the secondactive layer and the third metal layer, and covering the firstinsulation layer, and a pixel electrode layer formed on the passivationlayer, and contacting the third metal layer; wherein the firstinsulation layer is located between the first metal layer and the secondmetal layer and is also located between the first metal layer and thethird metal layer such that the first insulation layer is a gateinsulation layer that isolates the first active layer from the secondmetal layer and also isolates the first metal layer from the secondactive layer; wherein the first metal is in contact engagement with thefirst active and is separated from the second active layer by the firstinsulation layer; the second metal layer is separated from the firstactive layer and the first metal layer by the first insulation layer,and is also separated from the second active layer; and the third metallayer is in contact engagement with the second active layer, wherein theSwitching TFT that comprises the first active layer also comprises thesecond metal layer and a part of the first metal layer and the DrivingTFT that comprises the second active layer also comprises the thirdmetal layer and a part of the first metal layer; and wherein material ofthe first active layer and material of the second active layerrespectively are amorphous silicon and metal oxide semiconductor, LowTemperature Poly-silicon and amorphous silicon, Low TemperaturePoly-silicon and metal oxide semiconductor, or both metal oxidesemiconductor.